This disclosure generally relates to power conversion systems and methods for balancing at least a first DC link voltage and a second DC link voltage.
For most power conversion systems, switching type semiconductors (e.g., IGBTs) are commonly used and controlled to conduct current so as to accomplish a power conversion process (e.g., DC to AC and/or AC to DC). However, due to the voltage and/or current limitation of the semiconductors, it is difficult to achieve a high-power rating power conversion system. Attempts to increase voltage rating and current conduction capability have been made to handle high power.
In some power conversion systems, various new topologies are used to increase current conduction capability. For example, one topology that has been proposed is employing two or more power conversion modules with the same structure coupled in parallel in the power conversion system to increase current conduction capability. However, by increasing the load current, the conduction loss of the power conversion system increases significantly. Furthermore, it is difficult to use suitable cables and circuit breakers when the load current is too high.
In some power conversion systems, loads designed with an open-winding structure are commonly used to increase voltage rating. With the open-winding structure, the load can be supplied with power by dual power conversion modules in a push-pull manner, and each power conversion module handles half of the total voltage. In some applications, in order to control the power conversion modules in the same manner independently, it is desired that the DC link voltages in different power conversion modules can be controlled to be balanced. However, conventional strategies for balancing the DC link voltages are complex.
Therefore, it is desirable to provide systems and methods to address at least one of the above-mentioned problems.